1. Field of the Invention
The invention herein relates to drive belts for belt-driven tape devices, including magnetic tape cartridges.
2. Background of the Invention
Belt driven magnetic tape cartridges have been known for a number of years and are widely used commercially as backup storage devices for computers. Typical cartridges are those shown in U.S. Pat. Nos. 3,305,186; 3,514,049; 3,544,038 and 3,692,255 and French Pat. No. 1,297,446. In such cartridges the magnetic recording tape is driven by a thin continuous flexible belt which is in turn driven by a single reversible drive motor that provides rapid acceleration and deceleration of the recording tape in either direction. The tape used in such cartridges is extremely thin (as thin as 0.4 ml/0.010 mm) and is driven at high speeds (up to 120 inches per second/305 cm per second, or greater) and the data may be recorded on such tape at densites of about 20,000 flux reversals per inch (7900 reversals per cm). At these high tape speeds and recording densities tape-to-head contact and uniformity of tape speed are extremely critical. Such proper tape-to-head contact requires that the transmission of motion by the belt to the tape be uniform and consistent in speed, without significant belt slippage.
In recent years it has become apparent that the types of belts currently used or proposed for use do not provide such uniform motion transfer consistently over extended service lives. To this end, numerous techniques have been proposed to compensate for the belt failures. For instance, U.S. Pat. Nos. 4,466,564 and 4,58,189 disclose belts which have roughened surfaces to prevent tape slippage, U.S. Pat. No. 3,965,764 shows a cartridge utilizing two drive belts, and U.S. Pat. No. 3,305,186 discloses cartridges utilizing dual capstans turning at different speeds to impart tension to the belt. All of these systems, while operable and often used in commercial cartridges, have not completely solved the problem of non-uniform motion transfer to tapes, particularly as the belt ages.
In the past belts have been made of polyester materials, such as "Mylar.TM." polyester (U.S. Pat. No. 3,305,186) or polyester polyurethanes (U.S. Pat. No. 4,466,564). While such materials have been considered to be state of the art with respect to belt technology, it has been recognized that they have not been entirely satisfactory and research efforts have been devoted to mechanical means to compensate for the long term loss of tension and increasing slippage common to cartridges using the polyester or polyester urethane belts. Such mechanical compensation, however, adds complexity and cost to cartridges and provides another mechanism within the cartridge which can lead to cartridge failure.
It would therefore be of substantial advantage to have a belt which would maintain long term stability and constant tension during use and which could be readily and inexpensively fabricated.